Psyllium is a fibre obtained from the seeds of a plant called Plantago psyllium. It is widely used as a laxative to ease constipation when taken with water two or three times a day.
Do not take it if on a salt, potassium or sugar restricted diet, suffering from severe constipation with impacted faeces, or suffering from belly pain, nausea or vomiting.
The side effects are usually minimal but may include diarrhoea, belly discomfort and bloating. It can affect the absorption of other drugs for up to two hours after use.